Equine influenza virus has been recognized as a major respiratory pathogen in horses since about 1956. Disease symptoms caused by equine influenza virus can be severe, and are often followed by secondary bacterial infections. Two subtypes of equine influenza virus are recognized, namely subtype-1, the prototype being A/Equine/Prague/1/56 (H7N7), and subtype-2, the prototype being A/Equine/Miami/1/63 (H3N8). Presently, the predominant virus subtype is subtype-2, the H3N8 strain. It is now believed that this strain may be infecting canines and it can be quite virulent with canine fatality rates reported in some cases as high as 36%. It is possible that an interspecies transfer of the complete or a portion of the equine influenza virus to the dog resulted in a new canine specific influenza virus associated with acute respiratory disease. See, Transmission of Equine Influenza to Dogs (P. C. Crawford et al., Science 310, 482-485 (2005). There is a clear and convincing need for an effective vaccine to treat and prevent this new canine influenza.